Recombinant human thyrotropin (rhTSH) in the management of differentiated thyroid cancer

Recombinant human thyrotropin (rhTSH) has been evaluated in 38 patients wit h differentiated thyroid cancer. The patients had all been treated previous ly by operation and 31 had received radioiodine I-131. The patients continu ed to take thyroid hormone and changed to a low iodine diet for 14 days bef ore and throughout the week of testing. The rhTSH was injected intramuscula rly on two consecutive days, 74 MBq I-131 was administered on the next day and scintigraphy completed 48 h after that. TSH was measured before adminis tration of I-131, and thyroglobulin after the scan. All patients preferred this method to withdrawal of thyroid hormone, but 45% had mild symptoms inc luding headache and nausea. The average TSH was 127 mU.l(-1), and was inver sely related to the weight of the patients. Thirty-four had negative scans with a mean uptake of 0.06%. Thyroglobulin values above 10 ng.ml(-1) were f ound in seven patients, of whom four had similar findings when scanned afte r withdrawal of thyroid hormone. Of four with positive scans, two had undet ectable thyroglobulin. The rate of clearance of I-131 was compared in patie nts studied at 72 h who were hypothyroid and at 48 h in euthyroid patients given rhTSH and was found to be longer in the latter. We conclude that rhTS H can be used to stimulate thyroid tissue to trap I-131 and secrete thyrogl obulin. Both scan and thyroglobulin should be obtained. The method is well tolerated. ((C) 2000 Lippincott Williams & Wilkins).